Dogs and cats with long-standing skin or gastrointestinal troubles may be suffering food allergy. Once you’ve dispelled the myths surrounding food allergy, you’re ready to test. If you’re really serious about identifying a dietary allergen, forget expensive and unreliable blood tests, and go straight to a food elimination trial. If the response to this temporary diet is good, you’re already halfway to fingering the offending ingredient, excluding it, and solving your allergy problem. Unlike humans, who quickly grow bored and break dietary rules, pets often happily dine year-in, year-out, on the same old low-allergy diet.
What is your pet allergic to?
Diagnosing Food allergy: Blood test versus elimination diet
The use of blood tests for diagnosing food allergy is controversial. Commercial laboratories offer vets a blood testing service with an accuracy of up to 60%, at best. Many vet dermatologists view them as ‘absolutely useless’, resulting in false negatives and false positives, and elimination diet remains the gold standard for food allergy diagnosis.
If you’re lazy, impatient for an answer, and unphased by cost, do the blood test, but if excluding the identified allergen doesn’t seem to work, you’ll need to resort to an elimination trial anyway. I don’t recommend wasting your money on blood tests; spend it on an venison instead.
Principles of an elimination diet
Ingredients and recipes
Have as few ingredients as possible: preferably one source of protein, and one source of carbohydrate. The more ingredients, especially if commercial foods are included, the greater the likelihood an allergen may be inadvertently included in the elimination diet, ending in a false negative result.
Dogs should be fed a protein and carbohydrate that has rarely, if ever, been offered previously. Unusual protein sources are ideal, such as kangaroo, rabbit, duck, turkey, crocodile, or other game meats. Fish is a good choice as it’s also loaded with anti-allergy Omega-3’s. The offal of the protein source can be fed, but not that of other species. Protein can be served cooked or raw. Unusual carbohydrates are potatoes, rice or pulses.
An approximate recipe is 2 parts carbohydrate to 1 part protein. Protein content shouldn’t fall below 25%. While it’s tempting to incorporate other veggies, they’re not necessary in a short term trial.
Cats can receive a 100% protein diet, ideally containing a singular animal protein never previously fed. Kangaroo, rabbit, and turkey are good choices. Offal of the chosen species is ok. Carbohydrate, veggies and other ingredients are not necessary during the trial. If your cat is unwilling to eat the one species for the 6 to 8 week trial period, you may need to select 2 proteins, and alternate.
In both cat and dog, religiously exclude ingredients commonly used in commercial pet food such as beef, chicken, lamb (for dogs), soy, dairy, fish (for cats), wheat, oats, and corn. Dairy exclusion should encompass lactose-free milk products, manufactured for pets. Exclude all other potential food allergen sources including treats, rawhide and ear chews, flavoured medications, and bones (including those hidden in the garden).
Avoid commercial foods
Ingredient lists can’t always be relied upon. Supermarket brands can contain a Noah’s Ark of unlisted protein and other ingredients. If life’s already busy enough, preparing meals for the family, and 2 months of homecooking for the pet isn’t feasible, there are a handful of commercial foods recommended by vets for an elimination trial. These cost 20-30% more than regular pet foods, and can be used alone or supplementary to a novel, fresh meat diet:
- Hills Prescription Diet Z/d or D/d – rice/egg
- Eukanuba Response Formula FP – fish/potato
- Royal Canin Therapeutic, feline: pea/duck, pea/venison, pea/rabbit, pea/lamb, or Hypoallergenic HP
- Royal Canin Therapeutic, canine: potato/duck, potato/venison, potato/rabbit, potato/whitefish, or Hypoallergenic HP
If however, your pets skin or tummy trouble fails to improve on these commercial diets, it is still possible a home-cooked, novel protein diet may be effective.
When to do an elimination diet
Most food allergies are perennial and the flow of seasons offers no relief. However, when a pet suffers multiple allergies,and some seasonality is observed, conduct the elimination trial a time of year when the skin is usually bad, so a therapeutic benefit is easier to detect. Ask your regular vet: your pet’s medical records will reveal the yearly pattern.
Duration of an elimination diet
If no improvement is observed during the first 6 to 8 weeks, then you can give up and accept the depressing reality: the allergen originates outside the foodbowl.
If there’s a partial response, with some improvement, but no cure, you can increase your certainty by pushing out the trial to 10-12 weeks, and see how good an outcome is achievable.
If a good response is observed, start celebrating, but don’t overlook the opportunity to get more information with the challenge, described below.
Challenging after an elimination trial
Once you’ve established a diet which seems to have improved your pet’s health, it’s time to challenge with foods and look for symptoms to return. This is important, to firm-up our confidence the diet actually worked, and identify the exact allergen(s).
Understandably, once a food allergen is excluded and long-standing symptoms begin to clear, some pet owners are reluctant to enter a challenge phase. Relieved from chronic skin disease, they don’t ever wanna go back, and are happy to stick with the fish and potato, or other recipe, used in the trial. The trouble wih this approach is:
- Failure to identify the allergen, so all future dietary decisions are made in the dark. Fingering individual allergen(s) offers greater flexibility when selecting commercial foods and formulating homecooked recipes.
- Home cooked diets are often unbalanced. This is especially important in young, rapidly growing dogs, and cats living on 100% fresh meat diets. Having at least a small amount for commercial food in the daily ration is like giving a multivitamin. For more, see The Arguement for Dietary Diversity.
Two techniques for challenging
1) Scientifically test for the allergen, using staged re-introduction of ingredients, one-by-one. It can take between 2 days and 2 weeks for symptoms for reappear after introducing a food allergen, so don’t add a new ingredient more frequently than one every 2 weeks. Test all the major allergens starting with beef, chicken and lamb, fish for cats, and then check dairy, eggs, and pasta for wheat.
Cases of multiple allergy are rare, but if you discover one, continue to test the others. If no symptoms return, you have to question if the response to elimination diet was real, or if the skin problem spontaneously resolved, coincidentally. Once the allergen is fingered, you can start scrutinising labels and testing their claims wih your beef-detecting dog.
2) More crudely, experiment by offering commerical diets. As these represent a pot-purri of potential allergens, listed on packaging and unlisted contaminants, this process is very hit-and-miss. This option is often favoured by pragmatic pet owners, impatient to move onto kibble or tins ASAP, and relax after 2 months of labourious dietary rules.
Best to start with some of the higher quality, novel protein diets listed above, and then gradually move to cheaper, riskier petfoods, if desired. When symptoms return, guess which is the offending ingredient.
If you’re lucky, after 3 months of scouring butchers for exotic meats, boiling rice and potatoes, and getting dirty looks from a fussy cat, you may be liberated from the treadmill of derma-pharmaceuticals. If you see no such reward, it’s no waste of time, as you can slap-down the vet when ever he mentions the possibility of food allergy.
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